Fix build errors on CentOS 7 in rev.13712

Fix build errors on CentOS 7 in rev.13712

It turns out the RHEL and CentOS 7 STL definition does not quite match
up to official documentation of what their GCC version supports. In
particular the use of const_iterator on std::list containers.

Use auto instead of an explicit iterator. Allowing the compiler to select
whichever iterator is available and will work.